Auto merge of #6630 - xFrednet:0000-configuration-documentation, r=llogiq

Documentation for adding configuration to a lint and common abbreviations

This PR adds some commonly used abbreviations to the `basis.md` file and a guide on how to implement a configuration value for a lint.

* [Rendered `/doc/basics.md` (Abbreviation list)](https://github.com/xFrednet/rust-clippy/blob/0000-configuration-documentation/doc/basics.md#common-abbreviations)
* [Rendered `/doc/adding_lints.md` (Configuration value guide)](https://github.com/xFrednet/rust-clippy/blob/0000-configuration-documentation/doc/adding_lints.md#adding-configuration-to-a-lint)

I'm not sure if the guide is written in the best way. Style suggestions are appreciated. :upside_down_face:

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Again a big **thank you** for everyone who helped to collect the abbreviation list over on [zulip]. I had a lot of fun, and it was also very informative. Keep up the good work :upside_down_face:

[zulip]: https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/Common.20abbreviations.20in.20basics.2Emd/near/223548065
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changelog: none